Grounding outlet



April 1965 c. M. SMITH 3,178,666

GROUNDING OUTLET Filed June 22, 1962 2 Sheets-Sheet l Fig.4. 136

36 Fig. 6.

INVENTOR Clarence M. Smlth ATTORNEY WITNESSES Filed June 22, 1962 April 13, 1965 c. M. SMITH 3,178,666

GRQUNDING OUTLET 2 Sheets-Sheet 2 United States Patent Ofiice angers Patented Apr. 13, was

3,178,666 GROUNDING OUTLET Clarence M. Smith, Trumbull, 30nd, assignor, by mesne assignments, to Westinghouse Electric Corporation, a corporation of Pennsylvania Filed June 22, 1962, Ser. No. 204,431 6 Claims. (Cl. 339-44) The present invention relates to grounding outlets and more particularly to grounding outlets in which grounding contact means are protected against overstressing forces otherwise caused by a grounding prong during its insertion or removal.

The safety object in providing a grounding circuit for a load device is well known. Normally, when such a device is powered by connection through a power outlet, a grounding circuit is also established from the load device through the device power cord and the outlet to ground. Accordingly, the cord plug of the load device is usually provided with a grounding prong in addition to its power prongs and the outlet is necessarily provided A with a grounding contact for conductive engagement with the cord grounding prong.

The provision of reliable grounding performance by the grounding contact in an outlet is important at the present time and expectedly will acquire increased importance as and if usage of grounding outlets expands in the future. Thus, a user of an outlet should be justified in expecting that a grounding connection is in fact established when he connects a grounding plug to a grounding outlet One problem often encountered in presently marketed outlets is that, with continued outlet usage, the grounding contact becomes overstressed and deformed from grounding prong insertion and removal and therefore is substantially no longer structurally suitable for providing a grounding connection. If this fact goes undetected and if it precedes the termination of outlet life, the users expectation of a completed grounding circuit probably will not be met and an injury risk is created. The present invention is directed toward outlet structure so arranged as to prevent grounding contact deformation from overstressing forces and thereby to provide con tinued assuance of outlet grounding performance.

Accordingly, it is an object of the invention to provide a novel and eflicient grounding outlet in which means are provided for limiting an inserted grounding prong against deflecting a suitably supported grounding contact into an overstressed condition.

It is another object of the invention to provide a novel grounding outlet wherein these is provided a housing slot into which the grounding prong is substantially withheld from entry by abutment means and into which the grounding contact can be resiliently deflected without being overstressed upon engagement by the grounding prong.

A further object of the invention is to provide a novel grounding outlet wherein a grounding contact is deflectable into a housing slot to avoid being overstressed while a portion of the grounding contact is captivated within the housing slot 50 that the grounding contact is also limited in its movement outwardly of the housing slot.

Another object of the invention is to provide a novel grounding outlet wherein a yoke includes a slot for receiving the grounding contact when the latter is resiliently deflected a given amount by an inserted grounding prong and which includes abutment means for limiting the extent to which the grounding prong can resiliently deflect the grounding contact.

These and other objects of the invention will become more apparent upon consideration of the following detailed description along with the attached drawings, in which:

FIGURE 1 is a top plan view of a grounding outlet constructed in accordance with the principles of the ininvention;

FIG. 2 is a side elevational view of the grounding outlet shown in FIG. 1;

FIG. 3 is a view of a longitudinal section of the grounding outlet taken along the reference line IIIIII of FIG. 1, with portions of the grounding outlet being removed;

FIG. 4 is a view of a cross-section of the grounding outlet of FIG. 1 taken along the reference line IVIV of FIG. 3;

FIG. 5 is a fragmentary view, partially in section, of a grounding plug being inserted into a portion of the grounding outlet of FIG. 1;

FIG. 6 is a partial view of a longitudinal section of another grounding outlet constructed in accordance with the principles of the invention;

FIG. 7 is a partial top plan view of a yoke used in conjunction with another grounding outlet constructed in accordance with the principles of the invention; and

FIG. 8 is a perspective view of a portion of the yoke of FIG. 7.

In accordance with the broad principles of the invention, an electric outlet comprises an insulative housing and a conductive yoke to which a grounding contact is secured. The grounding contact includes an arm which extends along a grounding prong channel in the housing for engagement with an inserted grounding prong of a plug. The grounding contact arm is resiliently deflected by the inserted grounding prong into a suitably located recess in the housing and the extent to which such deflection occurs is limited by engagement of the grounding prong with abutment means. Overstressing forces on the grounding contact arm are thereby prevented and establishment of a grounding connection is substantially ensured for outlet life.

More specifically, in FIGS. 1-5 there is shown a grounding outlet 10 constructed in acordance with the principles of the invention. The grounding outlet 10 includes an elongated insulative housing 12 which can be molded by ordinary techniques in unitary form, as in this instance, or which can be provided in a form having plural parts. In addition, the grounding outlet 10 includes an elongated strap or yoke member 14 for mounting purposes.

The housing 12 is provided with one or more faced portions 16 adjacent its face or front side, and each of the faced portions 16 is provided with a pair of power blade slots 18 extending inwardly to suitably supported power terminals (not shown) within the housing 12. As shown in FIG. 2, each power terminal in the grounding outlet is provided with wire engaging means or a wire engaging screw 19. Further, each faced portion 16 is provided with a grounding prong slot 20 or 22, located in standardized relation to the power blade slots 18, and power blades 24 and grounding blade 26 of a grounding plug 28 (FIG. 5) can therefore all be received within the grounding outlet 10 through the blade slots 18 and 20 or 22 when the grounding plug 28 is seated upon either faced portion 16.

The yoke 14 is provided with a pair of oppositely located end ears 30 for supporting the grounding outlet 1t on an outlet box or the like by means of respective fasteners (not shown) passed through ear openings 32. In this particular embodiment of the invention, the yoke 14 wraps around the back side of the outlet housing 12 and for this purpose is provided with a pair of opposite end legs 34 (FIG. 3) and a back strap portion 36.

Means including a fastener 38 are provided for securing the yoke 14 to the housing 12. The fastener 38 is provided with a top portion 40 which seats on a housing shoulder 42 and is further provided with depending legs 44 which extend through the outlet housing 12 in a generally reetangularly cross sectioned channel 46. Each of the fastener legs 44 is provided with one or more tabs 48 which extend through an opening 50 in the yoke strap portion 36 and which are bent over to engage strap shoulders 52 so as to secure the yoke 14 to the housing 12. In addition, the yoke end legs 34 can each have side portion-s thereof seated in housing slots 54 for the purpose of holding the yoke end legs 34 against longitudinally outward deflection. The fastener 46 can also be provided with a threaded opening 56 for receipt of a face plate fastener.

Resilient grounding contact means are secured to the yoke 14, in this instance to the yoke strap portion 36, by any suitable means. For example, the grounding contact means 58, or a base portion 59 thereof, can be welded to the yoke strap portion as indicated by the reference character 61.

The grounding contact means 58 include a resilient contact arm 60 located in each of respective grounding prong channels 62 and 64 which communicate with the grounding prong slots 20 and 22 respectively in the faced portions 16. Thus, the grounding prong channels 62 and 64 extend longitudinally from the grounding prong slots 26 and 22 to the back side of the outlet housing 12 and the yoke strap portion 36. The grounding prong channel 62 is defined laterally substantially by insulative wall means 66 of the outlet housing 12.

The grounding prong channel 64, however, is bounded laterally in part by .insulative wall means 66 of the outlet housing 12 and in part by the adjacent yoke end leg 34.

A body portion 68 of the adjacent yoke end leg 34 defines the outer boundary of the grounding prong channel 64 longitudinally of the outlet housing 12, and one or more arms 76 extend generally longitudinally inwardly from the adjacent yoke end leg 34 so as partially to provide side boundary definition for the grounding prong channel 64 and further so as to provide for conductive engagement of a grounding wire by means of a screw 72 or the like. The yoke end leg 34 is further employed to provide the grounding prong slot 22 as one of desired or standard cross-sectional dimension, all as more fully set forth in US. Patent 3,032,736, granted to R. D. Howells, entitled Wiring Device, issued on May 1, 1962, and assigned to the present assignee.

The resilient grounding contact arms 60 are each pro-- vided as a part of a single member which forms the grounding contact means 58. Accordingly, a central base portion can be so formed as a part of the grounding contact means 58 as integrally to connect the base contact portions 59, and, in so doing, extend longitudinally of the housing 12 over the yoke shoulders 52 and between the fastener tabs 48. It is preferred that the grounding contact means 58 be formed from resilient wire to effect manufacturing economy. However, strip material can be employed so long as it is properly correlated with other elements of the outlet 10 to take ad vantage of the principles of the invention. If it is desired, of course, the grounding contact means 58 can comprise two or more elements so that the respective contact arms 60 form a part of the separate elements.

Each of the grounding contact arms 60 extends generally perpendicularly from the yoke strap portion 36 inwardly of the outlet housing 12 in the grounding prong channel 62 or 64. The grounding contact arms 60 are each aligned with a housing slot or groove 74 for resilient deflection therein upon engagement by the plug grounding prong 26. For the purpose of ensuring guidance of the grounding contact arms 60 into the respective ad acent slots 74, one or more portions 76 thereof can be formed to be located normally in the adjacent housing slot 74. In any event, it is necessary'that a contact portion 78 of the grounding contact arm 60 be located in the grounding prong channel 62 or 64 and outwardly of the housing slot 74 for contacting engagement with the grounding plug prong 26.

Upon insertion of the grounding plug prong 26 into My it) the grounding channel 62 or 64, the Prong 26 engages the grounding arm contact portion 73 and resiliently urges the latter toward the adjacent housing slot 74. Resilient responding force of the grounding contact arm 60 ensures a conductive engagement between the arm contacting portion 78 and the grounding prong 26. If the insertion of the grounding prong 26 is relatively abusive, that is for example, if it is canted as generally shown in FIG. 5, the deflection of the grounding contact arm 60 inwardly of the adjacent housing slot 74 is limited for the reason that housing shoulders 80 (FIG. 4) serve as abutment means against the plug prong 26. Thus, the resilient grounding contact means 58 can be so formed originally as to retain its resiliency without permanent deformation when the resilient grounding contact arm 60 is deflected to the maximum extent as limited by the eflect of the abutment means 80 on the grounding prong 26. It is noted of course that for the noted limiting action to take eflect, the housing slot 74 should be so sized in width as not to accept entry of the grounding prong 26.

It follows, therefore, that the original resiliency of the grounding contact arms 60 substantially continues to exist with continued usage of the grounding outlet 10. Conductive engagement of the grounding arm contact portion 78 with the plug prong 26 to establish a grounding connection is therefore obtainable with reasonable certainty for the life of the grounding outlet 10.

Another embodiment of the invention is shown in FIG. 6. This embodiment is similar to the embodiment described in connection with FIGS. 1-5 and therefore identical reference characters have been employed for identical elements. In this case, the resilient grounding contact arm 60 is provided with a prong contacting portion 82 and in addition an end portion 84 which is captivated in the adjacent housing slot 74 by means of a housing shoulder 86. Therefore, in this embodiment, resilient deflection of the grounding contact arm 60 is limited both inwardly and outwardly of the housing slot 74.

When the grounding contact 60 is resiliently deflected to its maximum extent in either of the embodiments so far described, the portion 76 or 84 located at the free end of the contact arm 60 can be engaged against the wall means 66 as indicated by the reference character 67 (FIG. 5) so as to characterize the resilient response of the contact arm 60 with action similar to that which characterizes a deflected beam supported adjacent each of its ends. Thus, the housing slot 74 should be of sufficient length to accommodate the longitudinal expansion of the contact arm 60 resulting from the interaction of the beam support forces and the prong deflecting forces.

In FIGS. 7 and 8 there is shown a portion of another embodiment of the invention. Thus, a yoke is shown for use with a suitable housing (not shown) having one or more parts in such a manner as to be secured, by any suitable and well known means, to the housing adjacent its front side rather than in the wrap around manner described in connection with the embodiments of the invention shown in FIGS. 1-6. Normally such a grounding outlet would comprise a base and cover parts, but a unitary housing might also be employed. In this application of the invention, resilient grounding contact means 102 have a portion 104 extending longiutdinally along a strap portion 106 of the yoke 100 and secured thereto by any suitable means such as by welding. The yoke strap portion 106 is provided with a grounding prong opening 108 and the grounding contact means 102 include a resilient contact portion extending integrally from the longitudinal grounding contact portion 104. An end portion 110 of the cotact portion 105 is located in and extends along a path through which the grounding prong 26 must pass for insertion through the yoke opening 108.

When the grounding prong 26 is inserted through the yoke opening 108 (namely, in a direction substantially perpendicular to the yoke strap portion 106), the prong Ii J 26 resiliently engages the grounding contact end portion 110 and resiliently deflects it inwardly toward or into a slot 112 located between abutment means or tabs 114 deflected outwardly of the plane of the yoke strap portion 106. The abutment means 114 are sufliciently close together to prevent entry of the grounding prong 26 into the slot 112 and therefore this limiting action prevents the grounding contact portion 110 from being overstressed by reason of excessive deflection. It is preferred that the tabs 114 be provided with suflicient length to terminate adjacent or substantially near a cross reference plane through bight portion 111 of the contact portion 105. This provision ensures abutment action against the grounding prong 26 along substantially the entire length of the contact end portion 110.

The grounding contact means 102 adjacent an end portion 101 of the yoke 100 can be secured to a laterally extending grounding wire engagement arm 103 rather than to the strap portion 106 as shown for the grounding contact means 102 in FIG. 8. Similar principles apply in either case.

In the foregoing remarks, the principles of the inven tion have been illustrated in connection with several embodiments thereof. Accordingly, it is desired that the invention be not limited by the embodiments described, but, rather, that it be accorded an interpretation consistent with the scope and spirit of its broad principles.

What is claimed is:

1. A grounding outlet comprising an elongated insulative housing member to which an elongated conductive yoke member i secured therealong for mounting purposes, said housing member having a slot through its face side for entry of a plug grounding prong into an elongated grounding prong channel located therein, said grounding prong channel extending transversely to said yoke, a resilient grounding contact having a portion secured to said yoke and having an arm inserted longitudinally within said grounding prong channel, at least a portion of said contact arm being located for resilient conductive engagement with said grounding prong, at least one of said members having another slot communicating with said channel and disposed for receiving said contact arm at least when the latter is subjected to deflection by said grounding prong, and respective abutment means located on opposite sides of said other slot and spaced from each other in sufliciently close relation to prevent said grounding prong from entering said other slot and excessively deflecting said contact arm inwardly of said other slot.

2. A grounding outlet comprising an elongated insulative housing member to which an elongated conductive yoke member is secured therealong for mounting purposes, said housing member having a slot through its face side for entry of a plug grounding prong intoan elongated grounding prong channel located therein, said grounding prong channel extending transversely to said yoke, a resilient grounding contact having a portion secured to said yoke and having an arm inserted longitudinally within said grounding prong channel, at least a portion of said contact arm located for resilient conductive engagement with said grounding prong, said housing member having another elongated slot communicating with said channel, said contact arm having another portion normally located in said other slot for guidance of said contact arm into said other slot when said contact arm is deflected by said grounding prong, and respective abutment means located on opposite sides of said other slot and spaced from each other in sufliciently close relation to prevent said grounding prong from entering said other slot and excessively defleeting said contact arm inwardly of said other slot.

3. A grounding outlet comprising an elongated insulative housing member to which an elongated conductive yoke member is secured therealong for mounting purposes, said housing member having a slot through its face side for entry of a plug grounding prong into an elongated grounding prong channel located therein, said grounding prong channel extending transversely to said yoke, a resilient grounding contact having a portion secured to said yoke and having an arm inserted longitudinally within said grounding prong channel, at least a portion of said contact arm located for resilient conductive engagement with said grounding prong, at least one of said members having another slot communicating with said channel and disposed for receiving said contact arm at least when the latter is subjected to deflection by said grounding prong, and abutment means so located adjacent said other slot as engageably to limit said grounding prong from excessively deflecting said contact arm inwardly of said other slot, said abutment means being formed by a pair of tabs deformed outwardly of said yoke member on opposite sides of said other slot and so spaced as to prevent entry of said grounding prong into said other slot.

4. A grounding outlet comprising an elongated insulative housing member to which an elongated conductive yoke member is secured therealong for mounting pu-1' poses, said housing member having a slot through its face side for entry of a plug grounding prong into an elongated grounding prong channel located therein, said grounding prong channel extending transversely to said yoke, a resilient wire grounding contact having a portion secured to said yoke and having an arm inserted longitudinally within said grounding prong channel, at least a portion of said wire contact arm located for resilient conductive engagement with said grounding prong, said housing having an elongated groove coextending longitudinally with said wire contact arm and communicating with said channel, said wire contact arm having another portion normally located in said groove for guidance of said wire contact arm into said groove when said wire contact arm is deflected by said grounding prong, and respective abutment means located on opposite sides of said groove and spaced from each other in sufliciently close relation to prevent said grounding prong from entering said groove and excessively deflecting said wire contact arm inwardly of said groove.

5. A grounding outlet comprising an elongated insulative housing member to which an elongated conductive yoke member is secured therealong for mounting purposes, said housing member having a pair of longitudinally spaced slots through its face side for entry of respective grounding prongs of respective plugs, a grounding prong channel extending transversely to said yoke and inwardly from each of said prong slots, resilient grounding contact means having a longitudinal portion thereof secured to said yoke and having respective arms inserted from each end thereof longitudinally and respectively within said grounding prong channels, at least a portion of each of said contact arms located for resilient conductive engagement with the respective grounding prongs, said housing member having another elongated slot communicating with each of said grounding prong channels and disposed for receiving respectively said contact arms at least when the latter are subjected to deflection by said grounding prongs, and respective abutment means located on opposite sides of each of said other slots and spaced from each other in sufliciently close relation to prevent said grounding prongs respectively from entering said other slots and excessively deflecting said contact arms inwardly of said other slots.

6. A grounding outlet comprising an elongated insulative housing member to which an elongated conductive yoke member is secured therealong for mounting purposes, said housing member having a pair of longitudinally spaced slots through its face side for entry of respective grounding prongs of respective plugs, a grounding prong channel extending transversely to said yoke and inwardly from each of said prong slots, resilient wire grounding contact means having a longitudinal portion thereof secured to said yoke and having respective arms inserted from each end thereof longitudinally and respectively Within said grounding prong channels, at least a portion of each of said Wire contact arms located for resilient conductive engagement with the respective grounding prongs, said housing having another elongated slot communicating With each of said grounding prong channels and disposed for receiving respectively said Wire contact arms at least when the latter are subjected to deflection by said grounding prongs, and respective abutment means located on opposite sides of each of said other slots and spaced from each other in sufiiciently close relation to prevent said grounding prongs respectively from entering said other slots and excessively deflecting said wire contact arms inwardly of said slots.

0 0 References Cited by the Examiner UNITED STATES PATENTS 1,927,245 9/33 Russell 339-44 2,686,297 8/54 Hutt 339-14 3,032,736 5/62 Howells 339-14 FOREIGN PATENTS 390,445 4/ 33 Great Britain.

499,811 5/34 Great Britain.

195,748 2/38 Switzerland.

331,339 7/58 Switzerland.

JOSEPH D. SEERS, Primary Examiner. 

1. A GROUNDING OUTLET COMPRISING AN ELONGATED INSULATIVE HOUSING MEMBER TO WHICH AN ELONGATED CONDUCTIVE YOKE MEMBER IS SECURED THEREALONG FOR MOUNTING PURPOSES, SAID HOUSING MEMBER HAVING A SLOT THROUGH ITS FACE SIDE FOR ENTRY OF A PLUG GROUNDING PRONG INTO AN ELONGATED GROUNDING PRONG CHANNEL LOCATED THEREIN, SAID GROUNDING PRONG CHANNEL EXTENDING TRANSVERSELY TO SAID YOKE, A RESILIENT GROUNDING CONTACT HAVING A PORTION SECURED TO SAID YOKE AND HAVING AN ARM INSERTED LONGITUDINALLY WITHIN SAID GROUNDING PRONG CHANNEL, AT LEAST A PORTION OF SAID CONTACT ARM BEING LOCATED FOR RESILIENT CONDUCTIVE ENGAGEMENT WITH SAID GROUNDING PRONG, AT LEAST ONE OF SAID MEMBERS HAVING ANOTHER SLOT COMMUNICATING WITH SAID CHANNEL AND DISPOSED FOR RECEIVING SAID CONTACT ARM AT LEAST WHEN THE LATTER IS SUBJECTED TO DEFLECTION BY SAID GROUNDING PRONG, AND RESPONSIVE ABUTMENT MEANS LOCATED ON OPPOSITE SIDES OF SAID OTHER SLOT AND SPACED FROM EACH OTHER IN SUFFICIENTLY CLOSED RELATION TO PREVENT SAID GROUNDING PRONG FROM ENTERING SAID OTHER SLOT AND EXCESSIVELY DEFLECTING SAID CONTACT ARM INWARDLY OF SAID OTHER SLOT. 